Heat exchanging element and process of making the same



HEAT EXCHANGING ELEMENT AND PROCESS OF MAKING THE SAME April 18, 1939. A. J. BERG El AL:

Filed Feb. 14, 1936 2 ftSSheet 1 8 wuc/who'o fill-"E50 J 5520, by/v 0. #055 W a W April 18, 1939. A. J. BERG ET AL 2,154,430

HEAT EXCHANGING ELEMENT AND PROCESS OF MAKING THE SAME Filed Feb. 14, 1955 '2 Sheets Sheet 2 1 1 .4 {I'I'l' 3mm 141 new J. .5586. Joy/V H055.

Patented Apr. '18, 1939 UNITED STATES PATENT OFFICE HEAT EXCHANGING ELEMENT AND PROCESS OF MAKING THE SAME Alfred J.

am, Portsmouth, N. 11., and John 0.

.Huse. United States Navy Application February 14, 1936, Serial No. 63,894

8 Claims. (01. 29-1573) (Granted under the act of March 3, 1883, as

7 amended April 30, 1928; 3'10 0. G. 757) Our invention relates primarily-t0 a new and useful heat or cold exchanging element and proces of making the same, although the same may be otherwise usefully employed.

; In the whole of the prior art in order to asso-.

' member. These operations are difficult and tedious operations requiring time and substantial expense as well as involve substantial wear upon the forming apparatus employed requiring its frequent and expensive replacement. vSuch forming stresses, where the strip is edgewise bent or formed to the desired shape directly upon the heater cold exchanging element, have required that the wall of such element be heavier and more expensive than otherwise required-in order to resist such forming pressure without deforming the wall of the heat exchanger element. Furthermore, the working temperature of such edgewise formationof the flat strip of metal to make the fin for the heat exchanger element has been inmany cases so intense as to destroy the normal cold rolled or cold worked characteristics of the metal of the strip, thus reducing its rigidity, resistance to deformation, as well as lowering its heat or cold exchanging capacity.

A further inherent difliculty in the edgewise formation of a flat strip of metal about an arched surface of a tube or cylinder is and always has been that even with ductile metals the width of such formed strip cannot exceed about one-half the diameter of the circle about the whole or a portion of which the strip may be bent edgewise. Wider strips have been so bent edgewise by one or more operations preforming the strip by edgewise bending to the desired or something near the desired diameter; Eachsuch pre-bending or coiling is but progressive stages with intervening annealing or normalizing the metal of the bent strip This involves substantial time and production costs. Andeven these auxiliary opera-' tions have their limits as to theheight of bent rib producible thereby.

We, with legions of others, have for many years heretofore been more 'or less extensive witnesses to lathe and other machine tools cutting a shaving, whose thickness may vary with the requirements of each particular job, and which shaving is frequently of great length. Heretofore, in shop practice the length of such shavings became a menace to the operators of the machinery and others due to their gyrations about the floor and elsewhere. These gyrations have occasioned in- Jury to the persons and property and are liable to occasion others. To reduce such menace such shavings have been cut in small pieces by the machine operator into short lengths as the shavings come from the machine and placed in the shavings-scrap receptacle. When the cutting 10 tool cuts upon a cylindrical surface the shavings are formed into a thin cylindrical helical flat coil. when a side cutting tool cuts the required depth commencing at an end of a cylindrical hollow bar the shaving is helical, thin and of 15 similar side surface dimensions to the end of the bar from which they were severed. In either case, such chips or shavings have been in steel as thin as .00014 of an inch of substantial width and hundreds of feet long without breaking.

.Other shavings have been aswide as 4 inches,

about .001. of an inch thick and many hundreds of feet long without breaking. Such shavings or chips have been heretofore scrap and of no utility except for re-melting.

One of the very substantial inventive concepts of our present invention is our concept that all of theheretofore indicated troubles and limitations. arising from forming a flat strip edgewise to the desired curvature and/or helix are overcome by cutting a shaving of metal of the desired thickness, curvature, formand width, and applying such cut shaving as the rib or flu of the heat exchanger element. In this case the center of the shaving is provided with an opening conforming to the exterior surface of the heat or cold exchanging member. Suchopening may be formed in the center of the end of the bar of metal from which such shaving is cut helically by a broad thin side cutting tool which may be of the usual construction. Such helical shaving or a portion of an end thereof is slipped over the heat exchanging element. Such shaving being of uniform width and thickness with thickness and consistency of metalv throughout its length will, upon being stretched, assume substantially uniform spaces between the helices, such spacing being proportionate to and controllable by such stretching stress. when the helical shaving is of the desired spacing between the helices the shaving may be secured at or near opposite ends of the tube or heat or cold exchanging member, such securement being by a drop of solder or otherwise as may be convenient or. desirable. Thereupon, the thus secured shaving is severed from its unsecured remainder. By this process of employing a shaving helically cut from the end of a bar of the desired metal and having the desired. end, external and internal, dimensions further revolutionize the making of finned heat or cold exchanging elements or tubes in thisthat heretofore the element or tube had to be placed in a lathe or like tool and rotated at substantial velocity while the strip of metal was being bent edgewise about or otherwise applied thereto, whereas, in accordance with our present invention the application of the fin or rib structure to the element or tube simplifies itself into a mere bench operation requiring no tools except those that may be necessary to solder or otherwise secure at desired intervals the cut or turned to final form \of our fin or rib structure to the element or tube. Thus, it becomes apparent that our method may be practiced by hand even upon a commercial basis. I

In such practice, however, the size and shape of the central opening in the chip or shaving must substantially conform to the contour of the heat or cold exchanging element or tube. size and shape of the central opening in the helical chip or shaving is larger than the contour of the heat or cold exchanging element or tube, the shaving in such case is rolled or otherwise subjected to inward pressure progressively applied about its exterior edge to produce a close physical contact between the inner edge of each helices of the helically coiled chip or shaving and exterior surface of the heat or cold exchanging element or tube to produce an efllcient heat or cold exchanging contact.

In the drawings illustrating our invention Figure l is an end elevation view of a bar of metal, which is cylindrical in the instance shown associated with a tool for cutting the requisite thickness of shaving therefrom;

Fig, 2 is a top plan view of the parts shown in Fi 1; 1

Fig. 3 is a top plan view of a heat or cold exchanging element or tube provided with a helical rib or fin cut from the bar indicated in Figs. 1 and 2;

Fig. 4 is an end elevation view of the heat or cold exchanging element or tube provided with the cylindrical helically coiled rib or fin aforesaid and a roller for insuring the firm contact of the inner edge of. the rib or fin with the exterior surface of the heat or cold exchanging element or tube as well as for securing the same together as hereinafter explainedi h Fig. 5 is a sectional elevation view on lines 555-5 of Fig. 4;

Fig, 6 is a central, vertical, sectional view of a portion of the roller shown in Figs. 4 and 5;

Fig. '7 is a top plan view of a portion of the periphery of the roller shown in Fig. 6; 1

Fig. 8 is a central, vertical, sectional view of portion of a heat or cold exchaging element or tube and the helical ribs formed of a specially cut shaving having an internal shoulder; and

Fig. 9 is a view of the cutting tool for cutting the shaving indicated in Fig. 8.

In the drawings in which like characters of reference indicate the same parts, l0 represents a bar of the metal desired to form the heat or cold exchanging rib or fin Ii. Said bar I0 is provided with acentral opening l2 which may be of such size and shape that the central opening through the shaving forming the heat or cold exchanging rib ii if such is. to conform to theexterior surface of the tube or other shaped member Where the 1 one end of shaving ii to the it, which may be hollow. The outer circumfer ence of the bar of metal shape desired for the rib ll. 4

The bar of metal in may be revolubly mounted in a lathe or other machine tool, not shown, having a relatively thin side cutting tool ll, Fig. 1.

it maybe oi the external heat or cold exchanging- 2, whose point extends into the central opening l2 in order to insure the complete severance of the shaving H from the bar It. As the bar II is rotated in the lathe or like machine tool, the cutter ltis moved longitudinally into the bar I. at such a rate as will afford the requisite thickness to each of the helical cut portions of the shaving, helices ll.

The bar I 0 may be either forged, cold worked, or cast metal of the kind adapted for and desired to be used to form the heat or cold exchanging rib ll of the heat or cold exchanging element Hi. This metal may be either ferrous or nonferrous, but we prefer to employ the non-ferrous metal for its greater ductility and freedom from substantial corrosion. Very satisfactory results have been obtained by us from non-ferrous metal, particularly copper and aluminum, and alloys in which such metal is a substantial content. Such results have been obtained with very thin fins it which may extend any desired height from the member l3 according to the exterior dimension of the bar I i from which they were cut. Satisfactory results have also been obtained where the bar it was of ferrous metal although the metal of the rib Ii was thicker in order to withstand protracted corrosion.

We have further found that the cutter ll in severing the shaving ii from bar it cold works the opposite lateral surfaces of the shaving, II. This cold working distorts the grain of the metal of the shaving and increases its surface density.

creases the height that the rib or fin ll, may project beyond the surface of the heat or cold exchanging member l3, increases the number of such ribs that may project from each unit of length of the heat or cold exchanging member it, increases the thermo-conductivity of the heat or cold exchanging element l3 provided with such ribs i i, and reduces the weight, cost and size of the required heat or cold exchanging unit comprising the desired plurality of the elements I! provided with the ribs ll.

After a desired length of the helical shaving II has been cut from the bar In, such shaving Ii may be severed from such bar and a portion thereof applied to theeIement l3. In such application one end of the shaving Ii is suitably secured at its inner edge to the .element [3. This secure-.

ment in Fig. 3 is designated as l5 and may represent solder or any other convenient securement. This securement is initially at the inner edge of desired point upon element [3. The adjacent portion of shaving H may then be slightly stretched by hand in order to obtain the requisite distance between each of the helices of the helical chip ll. Inasmuch as the chip II is uniformly dimensioned throughout its extent and of the same homogeneous metal, this spacing apart of the difierent helices of the helical shape II will beuniform. This chip ii may then like-wise be secured at least at the most distant point on element i3 from its initial securement and the residue of chip Ii severed. Our

' surface of the shaving ii,

method of making "the heat or cold exchanging element [3 with the chip I I may thus be practiced 'by hand as a bench operation disassociated from inner edges of each of the portions of chip II will be in firm thermal-contact with the exterior surface of the element l3 when the central opening l2 in bar I0 is of the appropriate size and shape. When such opening i2 is not of such appropriate size and shape, then each progressive portion of the shaving ii may be passed through the slit IS in roller I] having a central bearing l8 adapted to receive a suitable spindle, not shown. The wall i9 at the bottom of slot i6 isadapted to engage the peripheral edge of the shaving ii, while the sides of slot l6 approximately engage the lateral The roller i1 may be mounted to move in the desired path about or along the element l3. This path may be in a straight line or in a helix, as may be desired. When such straight line movement comprehends the formation of the shaving ii in a ring about the element l3, the shaving may be severed and itsadjacent substantially abutting edges left free or secured together. I

The movement of roller ll along the outer edge of shaving Ii presses the shaving Ii inward and sets the metal content of the shaving II in firm thermal contact with the outer surface of the element i3. This contact is sufficient in many cases to afford the requisite securement of the shaving ii to the element i3. In any instance where the. same is not a sufficient securement,

' solder may be employed or other convenient securements may be used. One of such other securements, which is conveniently applied simultaneously with the functioning of the roller i1, 'is to provide a plurality of very small bevelled projections 20 on the peripheral edge of roller i'i on opposite sides of the slot it. Such projections 2|! may be staggered relative to each other on 1 opposite sides of the slot i6. These projections 20 form slight indentations inthe exterior surface of the element l3 close to the opposite sides of the inner edge of shaving ii. Such slight indentations raise creasing projections 2|, each of which comprise metal ofthe element i3. At least the shaving I one surface of each of said slight projections 2| firmly engage opposite sides of the inner edge of Such projections 2| being staggered relative to each other upon opposite sides of the shaving tend to inwardly stress the portion of shaving |i extending between each pair of projections 2|. Such stress may extend to the degree of providing a slight kink in such portion of the shaving between each pair of projections 2| where the shaving ii is thin. Such stressing of the metal of shaving i between each pair'of projections 2| affords a simple inexpensive and highly efllcient securement of the shaving progressively throughout its extent along or about the element i3.

In heat exchanger, or other uses, where thin shavings i la are desired to be employed analogous to the shaving ii but with a contact with the surface of element i3 comprising an area of greater width than the normal thinness of the shaving iia, the shaving i la is cut with a curved inner edge I ib whose inner surface contacts with the outer surface of element |3-throughout a substantially wider area than the normal thinness stress due to the curved portion lib. The inner edge I lb of shaving Ila, in uses where such frictional and spring engagements may be deemed insuflicient securement to the element i3, additional securement may be afforded in either of the ways hereinbefore stated for the chip i I.

It will be apparent, at least to those skilled in this art, that our invention provides a simple, durable, inexpensive and highly emcient heat and cold exchanging article that may also be advantageously employed in other uses.

While we have shown the rib as being sheared or cut or severed from a round bar of metal, we do, not thereby desire to be misunderstood as limiting our invention to the shape of the bar from which the rib is cut, as the bar may be of other desired shapes such as square, hexagonal, octagonal, oblong, elliptical, and any other desired shape, with the central opening in the bar from which the fin is made, such opening being requiredonly when the rib is to surround an element; likewise the same grain distortion, cold working and other properties afforded by our invention to the rib, may be enjoyed even by a straight rib whose lateral surfaces have been sheared or cut from a block of metal of the requisite dimensions.

The Government of the United States may make and use and have made for its use for governmental purposes the foregoing invention without the payment of any royalties thereon or there- Having now so fully described our invention that others skilled in the art may therefrom make and use the same, what we claim is:

1. The method of making a helical heat exchange fln comprising progressively and substantially uniformly cutting a bar of high heat conductivity metal continuously at its end and in the direction of its length to directly form by the having a substantially uniform thickness throughout and a height equal to many times its thickness, the said fln being adapted to be secured to a heat exchange element.

2. The method of making a helical heat exchange fln comprising progressively and substantially uniformly cutting a longitudinally apertured bar of high heat conductively metal continuously at its end and in the direction of its length to directly form by the cutting operation an apertured helical heat exchange fin having a substantially uniform thickness throughoutand a height equal to many times its thickness, the said fin being adapted to be secured to a heat exchange element.

3. The method of making a heat exchange device including a heat exchange element provided with a helical heat exchange fln secured thereto, comprising progressively cutting a bar of high heat conductivity metal continuously at its end and in the'direotion of its length to directly form by the cutting operation a helical heat exchange fin, and securing the said. fin

' so formed to a heat exchange element.

aeralsurfacesofsaidfin 4. The method of making a heatemhange device including a heat exchange element provided with a helical heat exchange fin secured thereto, comprising progressively and substan-' a heat exchange element and securing the fin I thereto.

5. A cut helical heat exchange fin of high heat conductivity metal adapted to be secured to a heat exchange element, said fin having a substantially uniform thickness throughout and a height equal to many times its thickness, the entire lateral surfaces 01 said fin being formed by a cutting operation and cold worked by the cutting. u

6. A heat'exchange device comprising in combination a heat exchange element and a cut apertured helical fin of high heat conductivity positioned about and secured to said heat exchange element, said fin having a substantially uniform thickness throughout and a height equal to manytimes its thickness, the entire latbeing formed by a cutting operation and cold worked by the cutting.

7. The method of making a heat exchange-deheat conductivity 7 worked by the cutting.

viceincluding a heat exchange element provid-' ed withva helical heat exchange; fin secured thereto having a height greater than one-half the diameter of the aforesaid element, comprising progressively and substantially uniformly cutting a longitudinally apertured bar of high metal of an outer diameter reater than twice its inner diameter continuously at its end and in the direction of its length to directly form by the cutting operation an apertured helical heat exchange fin having a substantially uniform thickness throughout and a height greater than one-half the diameter of the heat exchange element to which it is to be secured, positioning the said fin so formed about a heat exchange element having an outer diameter substantially equal to the inner diameter of the aforesaid fin and securing the fin at its inner periphery thereto.

8. A heat exchange device comprising in combination a heat exchange element and a cut apertured helical fin of high heat conductivity positioned about and secured to said heat exchange element, said fin having' a substantially uniform thickness throughout and a height greater than one-half the diameter of the aforesaid element, the entire lateral surfaces of said fin being formed by a cutting operation and cold ALFRED J. BERG. JOHN O. HUSE. 

